<!DOCTYPE html>
<!-- Any copyright is dedicated to the Public Domain.
   - http://creativecommons.org/publicdomain/zero/1.0/ -->

<html>
  <style>
  summary {
    display: inline; /* ::first-line appiles only to inline element. */
  }

  details::first-line {
    color: blue;
  }
  </style>
  <body>
    <details open>
      <summary>Summary
        <!-- Need ib-split so that the summary has multiple frames. -->
        <div>Block in summary</div>
      </summary>
      <span>This is the details.</span>
    </details>
  </body>
</html>
